Python zip函数

This function returns a list of tuples, where the i-th tuple contains the i-th element from each of the argument sequences or iterables. The returned list is truncated in length to the length of the shortest argument sequence. When there are multiple arguments which are all of the same length, zip() is similar to map() with an initial argument of None. With a single sequence argument, it returns a list of 1-tuples. With no arguments, it returns an empty list.

The left-to-right evaluation order of the iterables is guaranteed. This makes possible an idiom for clustering a data series into n-length groups using zip(*[iter(s)]*n).

zip() in conjunction with the * operator can be used to unzip a list:

pythonAPI上面说的

下面自己上例子:

x=[1,2,3]
y=[4,5,6]
z=[7,8,9]

print zip(x)

print zip(x,y)

print zip(x,y,z)

结果是：

[(1,), (2,), (3,)]
[(1, 4), (2, 5), (3, 6)]
[(1, 4, 7), (2, 5, 8), (3, 6, 9)]

可以看出zip是把同一维度的数据放在一个list中

w= zip(x,y,z)

for a,b,c in w:
    print 'a:{0},b:{1},c:{2}'.format(a,b,c)

结果是：

a:1,b:4,c:7
a:2,b:5,c:8
a:3,b:6,c:9

for是把list中的tuple中的每个元素输出

print type(w), type(w[1])

<type 'list'> <type 'tuple'>

x=[1,2,3]
y=[4,5,6]
z=[7,8,9]

w= zip(x,y,z)
print w
print zip(*w)

结果：

[(1, 4, 7), (2, 5, 8), (3, 6, 9)]
[(1, 2, 3), (4, 5, 6), (7, 8, 9)]

这是zip(*w)是把功能返回去而已